Reagent injector

ABSTRACT

An injector for injecting a reagent into an exhaust stream includes an outer tube extending through an electromagnet and surrounding an inner tube. A first end of the inner tube is sealingly fixed to an inner surface of the outer tube. A guide member and an orifice plate are each sealingly fixed to the inner surface of the outer tube. A second end of the inner tube is aligned by the guide member. A moveable valve member includes a pintle head guided by the inner surface of the outer tube to align the valve member with an orifice extending through the orifice plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/465,281, filed on May 7, 2012. The entire disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The present disclosure relates to injector systems and, moreparticularly, relates to an injector system for injecting a reagent,such as an aqueous urea solution, into an exhaust stream to reduceoxides of nitrogen (NO_(x)) emissions from diesel engine exhaust.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art. Lean burn engines provideimproved fuel efficiency by operating with an excess of oxygen, that is,a quantity of oxygen that is greater than the amount necessary forcomplete combustion of the available fuel. Such engines are said to run“lean” or on a “lean mixture.” However, this improved or increase infuel economy, as opposed to non-lean burn combustion, is offset byundesired pollution emissions, specifically in the form of oxides ofnitrogen (NO_(x)).

One method used to reduce NO_(x) emissions from lean burn internalcombustion engines is known as selective catalytic reduction (SCR). SCR,when used, for example, to reduce NO_(x) emissions from a diesel engine,involves injecting an atomized reagent into the exhaust stream of theengine in relation to one or more selected engine operationalparameters, such as exhaust gas temperature, engine rpm or engine loadas measured by engine fuel flow, turbo boost pressure or exhaust NO_(x)mass flow. The reagent/exhaust gas mixture is passed through a reactorcontaining a catalyst, such as, for example, activated carbon, ormetals, such as platinum, vanadium or tungsten, which are capable ofreducing the NO_(x) concentration in the presence of the reagent.

An aqueous urea solution is known to be an effective reagent in SCRsystems for diesel engines. However, use of such an aqueous ureasolution involves many disadvantages. Urea is highly corrosive and mayadversely affect mechanical components of the SCR system, such as theinjectors used to inject the urea mixture into the exhaust gas stream.Urea also may solidify upon prolonged exposure to high temperatures,such as temperatures encountered in diesel exhaust systems. Solidifiedurea will accumulate in the narrow passageways and exit orifice openingstypically found in injectors. Solidified urea may also cause fouling ofmoving parts of the injector and clog any openings or urea flowpassageways, thereby rendering the injector unusable.

Some reagent injection systems are configured to include a pump, asupply line and a return line such that aqueous urea is continuouslypumped to minimize solidification and also transfer heat from theinjector to the aqueous urea stored at a remote location. Theseinjectors are typically equipped with an inlet coupled to the supplyline and a spaced apart outlet coupled to the return line where both theinlet and the outlet are positioned on an opposite side of anelectromagnet as the injector orifice. While injectors configured inthis manner have functioned sufficiently in the past, concerns may ariseregarding the pumped fluid interrupting the magnetic circuit anddecreasing the efficiency of the solenoid. An increased current, coildiameter, wire diameter and/or number of coil turns may be required toaccount for the inefficient circuit.

Other concerns may arise regarding previously provided injectorsregarding cost, complexity and leakage of the fluid to be pumped eitherthrough the injection orifice or some other joint between injectorcomponents. Accordingly, it may be desirable to provide an improvedreagent injector addressing some or all of these concerns.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

An injector for injecting a reagent into an exhaust stream includes anouter tube extending through an electromagnet and surrounding an innertube. A first end of the inner tube is sealingly fixed to an innersurface of the outer tube. A guide member and an orifice plate are eachsealingly fixed to the inner surface of the outer tube. A second end ofthe inner tube is aligned by the guide member. A moveable valve memberincludes a pintle head guided by the inner surface of the outer tube toalign the valve member with an orifice extending through the orificeplate.

An injector for injecting a reagent into an exhaust stream includes anelectromagnet coupled to a housing. A slot disc includes a plurality ofcircumferentially spaced apart swirl ports extending therethrough. Theslot disc also includes a swirl slot extending between each swirl portand terminating at a swirl chamber. Each swirl slot includes asubstantially linear portion and a circular portion where the circularportions define an outer diameter of the swirl chamber. An orifice plateincludes an orifice and is fixed to the slot disc. A valve member ismoveable within the housing between a closed position where reagent isrestricted from exiting the orifice and an open position where reagentis allowed to pass through the orifice based on an energization of theelectromagnet. Reagent is pumped through the swirl ports, the swirlslots and the swirl chamber when the valve member is in the openposition.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic depicting an exemplary exhaust aftertreatmentsystem including an electromagnetically controlled reagent injectorconstructed in accordance with the teachings of the present disclosure;

FIG. 2 is an exploded perspective view of the reagent injector;

FIG. 3 is a cross-sectional view taken through the injector depicted inFIG. 2;

FIG. 4 is another cross-sectional view taken through a cartridgeassembly of the injector depicted in FIGS. 2 and 3;

FIG. 5 is an enlarged fragmentary cross-sectional view of the injector;

FIG. 6 is a fragmentary perspective view of a portion of the previouslydepicted injector;

FIG. 7 is a fragmentary sectional perspective view of the injector;

FIG. 8 is a perspective view of an assembly tool with components of theinjector; and

FIG. 9 is a plan view of the components with the assembly tool.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

It should be understood that although the present teachings may bedescribed in connection with diesel engines and the reduction of NO_(x)emissions, the present teachings may be used in connection with any oneof a number of exhaust streams, such as, by way of non-limiting example,those from diesel, gasoline, turbine, fuel cell, jet or any other powersource outputting a discharge stream. Moreover, the present teachingsmay be used in connection with the reduction of any one of a number ofundesired emissions. For example, injection of hydrocarbons for theregeneration of diesel particulate filters is also within the scope ofthe present disclosure. For additional description, attention should bedirected to commonly-assigned U.S. Pat. No. 8,047,452, issued Nov. 1,2011, entitled “Method And Apparatus For Injecting Atomized Fluids”,which is incorporated herein by reference.

With reference to the Figures, a pollution control system 8 for reducingNO_(x) emissions from the exhaust of an internal combustion engine 21 isprovided. In FIG. 1, solid lines between the elements of the systemdenote fluid lines for reagent and dashed lines denote electricalconnections. The system of the present teachings may include a reagenttank 10 for holding the reagent and a delivery module 12 for deliveringthe reagent from the tank 10. The reagent may be a urea solution, ahydrocarbon, an alkyl ester, alcohol, an organic compound, water, or thelike and can be a blend or combination thereof. It should also beappreciated that one or more reagents may be available in the system andmay be used singly or in combination. The tank 10 and delivery module 12may form an integrated reagent tank/delivery module. Also provided aspart of system 8 is an electronic injection controller 14, a reagentinjector 16, and an exhaust system 18. Exhaust system 18 includes anexhaust conduit 19 providing an exhaust stream to at least one catalystbed 17.

The delivery module 12 may comprise a pump that supplies reagent fromthe tank 10 via a supply line 9. The reagent tank 10 may bepolypropylene, epoxy coated carbon steel, PVC, or stainless steel andsized according to the application (e.g., vehicle size, intended use ofthe vehicle, and the like). A pressure regulator (not shown) may beprovided to maintain the system at predetermined pressure setpoint(e.g., relatively low pressures of approximately 60-80 psi, or in someembodiments a pressure of approximately 60-150 psi) and may be locatedin the return line 35 from the reagent injector 16. A pressure sensormay be provided in the supply line 9 leading to the reagent injector 16.The system may also incorporate various freeze protection strategies tothaw frozen reagent or to prevent the reagent from freezing. Duringsystem operation, regardless of whether or not the injector is releasingreagent into the exhaust gases, reagent may be circulated continuouslybetween the tank 10 and the reagent injector 16 to cool the injector andminimize the dwell time of the reagent in the injector so that thereagent remains cool. Continuous reagent circulation may be necessaryfor temperature-sensitive reagents, such as aqueous urea, which tend tosolidify upon exposure to elevated temperatures of 300° C. to 650° C. aswould be experienced in an engine exhaust system.

Furthermore, it may be desirable to keep the reagent mixture below 140°C. and preferably in a lower operating range between 5° C. and 95° C. toensure that solidification of the reagent is prevented. Solidifiedreagent, if allowed to form, may foul the moving parts and openings ofthe injector.

The amount of reagent required may vary with load, exhaust gastemperature, exhaust gas flow, engine fuel injection timing, desiredNO_(x) reduction, barometric pressure, relative humidity, EGR rate andengine coolant temperature. A NO_(x) sensor or meter 25 is positioneddownstream from catalyst bed 17. NO_(x) sensor 25 is operable to outputa signal indicative of the exhaust NO_(x) content to an engine controlunit 27. All or some of the engine operating parameters may be suppliedfrom engine control unit 27 via the engine/vehicle databus to thereagent electronic injection controller 14. The reagent electronicinjection controller 14 could also be included as part of the enginecontrol unit 27. Exhaust gas temperature, exhaust gas flow and exhaustback pressure and other vehicle operating parameters may be measured byrespective sensors.

With reference to FIGS. 2-7, reagent injector 16 will be furtherdescribed. Reagent injector 16 includes a cartridge body assembly 50, anelectromagnet assembly 52, a mounting plate 54, an inlet assembly 56,and an outlet assembly 58. Cartridge body assembly 50 includes a tubularouter body 60 fixed to a tubular inner body 62. Outer body 60 includes afirst end 64 and an opposite second end 66. A plurality ofcircumferentially spaced apart apertures 68 extend through outer body60. Outer body 60 includes an inner surface 72 defining a substantiallycylindrical bore 73 having a reduced diameter portion 75. Outer body 60also includes an enlarged diameter portion 74. Inner body 62 is asubstantially hollow tube having a bore 78 including a first reduceddiameter portion 80 and a second enlarged diameter portion 82. Enlargeddiameter portion 82 is sized to closely fit within reduced diameterportion 75 of outer body 60. Inner body 62 is fixed to outer body 60using a laser welding process. Laser weld 86 circumferentially extendsto form a seal between inner body 62 and outer body 60 such that a lowerchamber 90 is separated from an upper chamber 92. Lower chamber 90 formsa portion of a supply passage.

Cartridge assembly 50 also includes a lower guide 96, a slot disc 98,and an orifice plate 100. Lower guide 96 includes a substantiallycylindrical outer surface 102 sized to closely fit within reduceddiameter portion 75 of outer body 60. A bore 104 extends through lowerguide 96 to allow fluid to pass therethrough. Bore 104 includes anenlarged diameter portion 106 sized to receive inner body 62. Aplurality of inlet ports 110 are circumferentially spaced apart from oneanother extending through cylindrical outer surface 102 in communicationwith bore 104. A plurality of bypass ports 112 interconnect inlet ports110 with bore 78 of inner body 62. Bore 104 also includes a guideportion 116. It is contemplated that lower guide 96 is metal injectionmolded from a material such as 17-4 MIM.

Slot disc 98 may be constructed from a plate or a sheet of materialhaving a closely controlled thickness. Slot disc 98 may be constructedfrom 304 stainless steel and include a plurality of stamped or laser cutslots 120. Alternatively, slot disc 98 may be metal injection moldedfrom 17-4 MIM. Slots 120 are arcuately shaped and circumferentiallyspaced apart from one another. Slots 120 are oriented to be in fluidcommunication with inlet ports 110. To assure this orientation, one ofslots 120 identified as 120 a circumferentially extends a greater arclength than the other slots. This asymmetrical feature is used incombination with an assembly tool 124, depicted in FIGS. 8 and 9, toassure that slot disc 98 is fixed to lower guide 96 at a desiredorientation. Assembly tool 124 includes a plurality of circumferentiallyspaced apart posts 126 each including a tang 128 extending therefrom.One tang, identified as tang 128 a circumferentially extends a greaterarc length than the other tangs 128. To assemble lower guide 96 and slotdisc 98, lower guide 96 is placed within assembly tool 124.Subsequently, slot disc 98 is oriented to align slot 120 a with tang 128a to allow slot disc 98 to engage lower guide 96. Subsequently, electronbeam welding fixes slot disc 98 to lower guide 96. A subassembly oflower guide 96 and slot disc 98 may be used for assembly of cartridgeassembly 50.

Slot disc 98 includes a plurality of swirl slots 132 in fluidcommunication with slots 120. Each of swirl slots 132 includes asubstantially linear portion 134 and a circular portion 136. Swirl slots132 impart a swirling motion to injected reagent passing through inletports 110 and slots 120.

Orifice plate 100 includes an orifice 140 coaxially aligned with aconical valve seat 142. Circular portions 136 of swirl slots 132 definea circle that is coaxially aligned with orifice 140 and conical valveseat 142. Orifice plate 100 includes an outer cylindrical surface 148that is sized to closely fit with reduced diameter portion 75 of outerbody 60. Orifice plate 100 is fixed to outer body 60 using an electronbeam welding process that sealingly couples orifice plate 100 to outerbody 60.

A valve member 154 is slidably positioned within enlarged portion 74 ofbore 73. Valve member 154 includes an elongated pintle 156 having aconically shaped first end 158 and an opposite second end 160. First end158 is selectively engageable with valve seat 142 of orifice plate 100to define a sealed and closed position of valve member 154 when seated.An unsealed, open position exists when pintle 156 is spaced apart fromvalve seat 142. Valve seat 142 may be conically or cone-shaped as shownto complement the conical first end 158 of pintle 156 to restrict theflow of reagent through orifice 140. Depending on the application andoperating environment, pintle 156 and orifice plate 100 may be made froma carbide material, which may provide desired performancecharacteristics and may be more easily and cost-effectivelymanufactured. Carbide may provide additional advantages, such asinsensitivity to brazing temperatures that may range from 870-980° C.,as opposed to carbon steels, which may distemper. Carbide may alsoprovide an increased surface hardness when compared to the hardnessachievable with most other steels. Carbide may also be advantageous withregard to overall wear resistance. Orifice plate 100 may alternativelybe constructed from a precipitation hardened material, CPM S90V or 440Cstainless steel.

A pintle head 162 is fixed to second end 160 of pintle 156. Pintle head162 is slidably positioned within enlarged portion 74 of bore 73 andincludes a plurality of circumferentially spaced apart apertures 170extending therethrough. A running-class slip fit between pintle head 162and inner surface 72 provides an upper guide for valve member 154 totranslate along an injection axis 155. A lower valve member guide isformed at the sliding interface between pintle 156 and guide portion 116of lower guide 96. Based on the provision of inner surface 72 as a datumfor orifice plate 100, lower guide 96, and pintle head 162, valve member154 is accurately aligned with valve seat 142 and orifice 140.

A pole piece 174 is sized to be received within bore 73. Pole piece 174is fixed to outer body 60 using a process such as electron beam weldingor laser welding. Elongated pole piece 174 includes a central bore 184extending therethrough. Central bore 184 is coaxially aligned with bore73. A restrictor plate 186 is positioned within a pocket 187 of polepiece 174. A counterbore 190 inwardly extends from an end 192 of polepiece 174. A compression spring 194 is positioned within counterbore 190in biased engagement with pintle head 162 to urge valve member 154 intoengagement with valve seat 142.

Electromagnet assembly 52 includes a coil of wire 200 wrapped around abobbin 202. Pintle head 162 is constructed from a magnetic material suchas 430 stainless steel such that electrical energization of coil 200produces a magnetic field urging pintle head 162 toward pole piece 174.When coil 200 is energized, first end 158 of pintle 156 becomesdisengaged from valve seat 142 to allow reagent to flow through orifice140. Power may be provided to coil 200 via access to a receptacle 206 ofan overmolded housing 208, for example, in response to a signal fromelectronic injection controller 14.

A flux frame 210 includes a tube 212 surrounding bobbin 202 and coil200. An end cap 214 extends from tube 212 to an outer surface of outerbody 60. Mounting plate 54 provides the remaining portion of flux frame210. Mounting plate 54, however, is not a portion of an overmoldedsubassembly including coil 200, bobbin 202, tube 212, end cap 214,receptacle 206 and overmolded housing 208. Housing 208 includes a tang216 sized and shaped for receipt within a key way 218 of mounting plate54. A relative angular orientation between receptacle 206 and an inletboss 220 of mounting plate 54 is assured once tang 216 resides withinkey way 218.

Cartridge assembly 50 extends through electromagnet assembly 52 as wellas mounting plate 54. Outer body 60 is laser welded to mounting plate 54proximate a mounting plane 222 of mounting plate 54 as well as at alocation proximate pintle head 162. The laser welds extenduninterruptedly 360 degrees to form a seal between mounting plate 54 andouter body 60. No additional elastomeric seals are required.

Inlet assembly 56 includes a 300 series stainless steel tube 230 and aninlet filter 232. Inlet tube 230 is fixed to boss 220 of mounting plate54 by a process such as laser welding. Inlet tube 230 is in fluidcommunication with an inlet passageway 234 extending through mountingplate 54. Inlet passageway 234 is in fluid communication with each ofapertures 68 extending through outer body 60 and chamber 90 or supplypassage 90.

Outlet assembly 58 includes a 300 series stainless steel outlet tube 236and an outlet filter 238. Outlet tube 236 includes a first end 240 sizedto be received within a pocket 242 formed in overmolded housing 208.Outlet tube 236 is laser welded to outer body 60 to retain electromagnetassembly 52 between outlet assembly 58 and mounting plate 54. Outlettube 236 is in fluid communication with central bore 184 of pole piece174.

A closed loop reagent fluid path is provided when pintle 156 of reagentinjector 16 is in the closed position. Reagent is provided from reagenttank 10 via delivery module 12 to inlet tube 230. Reagent passes throughinlet filter 232, inlet passageway 234 and aperture 68 to enter supplypassage or lower chamber 90. Reagent continues to flow through inletports 110 and bypass ports 112 to enter a return passage or bore 78 ofinner body 62. Pressurized reagent continues to flow through apertures170 of pintle head 162 and central bore 184 of pole piece 174.Restrictor plate 186 includes an aperture 244 through which the returnflow rate of reagent is controlled. Outlet tube 236 is in receipt of thereagent returning to tank 10. When reagent is not being injected intothe exhaust system, the reagent is continuously pumped to flow throughlower guide 96 and transfer heat from orifice plate 100 to the reagentstored in tank 10.

When electromagnet assembly 52 is energized, pintle 156 is moved fromvalve seat 142. Pressurized reagent in communication with slots 120flows through each of swirl slots 132 to enter a swirl chamber 250defined by circular portions 136, lower guide 96, pintle 156 and orificeplate 100. Based on the pressure differential between orifice 140 andswirl slots 132, as well as the tangential relationship of swirl slots132 to swirl chamber 250, a rapidly moving circular reagent motion isinduced. The lower pressure at orifice 140, combined with thepressurized reagent moving in a swirling fashion, creates a finelyatomized spray exiting orifice 140. Reagent that does not exit orifice140 continues to be recirculated as previously described.

It should be appreciated that it may be desirable to vary the sprayangle at which reagent exits orifice 140. It has been discovered that bychanging the diameter of the circle defined by circular portions 136 andtherefore the diameter of swirl chamber 250, the total included angle ofthe reagent spray exiting orifice 140 may also be varied. For example,the number of slots, slot width, and plate thickness can be varied toachieve a desired spray angle. As such, a family of injectors may beprovided having each of the same components with the exception of adifferent slot disc having geometry tailored to produce the desiredspray angle. In comparison with machining relatively complex injectioncomponents, providing a family of different slot discs is inexpensiveand simple.

Furthermore, the foregoing discussion discloses and describes merelyexemplary embodiments of the present disclosure. One skilled in the artwill readily recognize from such discussion, and from the accompanyingdrawings and claims, that various changes, modifications and variationsmay be made therein without departing from the spirit and scope of thedisclosure as defined in the following claims.

What is claimed is:
 1. An injector for injecting a liquid, comprising:an electromagnet; an inner tube including a substantially constant wallthickness; an outer tube including a substantially constant wallthickness, the outer tube extending through the electromagnet andsurrounding the inner tube; a guide member positioned within the outertube; a slot disc including asymmetrically shaped swirl slots, the slotdisc being positioned within the outer tube and in contact with theguide member, the guide member including circumferentially spaced apartinlet ports in communication with the swirl slots, the inlet ports andthe asymmetrical swirl slots being adapted for alignment with each otherby assembly tool, wherein the guide member and the slot disc are fixedto the outer tube after alignment with each other by the tool; and amoveable valve member extending through the inner tube.
 2. The injectorof claim 1, wherein the inner tube and the outer tube at least partiallydefine a supply passage through which the liquid flows to the inletports.
 3. The injector of claim 2, wherein the outer tube includes anaperture in receipt of the liquid, the aperture being axially locatedbetween the electromagnet and the orifice.
 4. The injector of claim 3,further including a return passage extending through the valve memberand the inner tube to allow recirculation of the liquid.
 5. The injectorof claim 4, further including an orifice plate including an orifice,wherein the slot disc is positioned between the orifice plate and theguide member, the swirl slots being in fluid communication with thesupply passage and the orifice.
 6. The injector of claim 5, wherein theguide member includes a bypass port providing fluid communicationbetween the supply passage and the return passage.
 7. The injector ofclaim 1, further including a pole piece positioned adjacent to the valvemember and fixed to an inner surface of the outer tube.
 8. The injectorof claim 7, wherein the pole piece includes a bore in receipt of aspring biasing the valve member away from the pole piece.
 9. Theinjector of claim 1, wherein the electromagnet includes a coil of wirewrapped around a bobbin, a flux frame surrounding the wire and a plastichousing encapsulating the wire, bobbin and flux frame.
 10. The injectorof claim 1, further including an orifice plate, wherein the outer tube,the inner tube, the guide member, the slot disc, and the orifice plateare coupled to one another without threaded interconnections.
 11. Theinjector of claim 1, wherein the injector includes a cartridge assemblycomprising an orifice plate, the outer tube, the inner tube, the guidemember, and the slot disc, wherein the cartridge assembly does notinclude an elastomeric seal.